usb: gadget: f_ncm: Fix NTP-32 support

When connecting a CDC-NCM gadget to an host that uses the NTP-32 mode,
or that relies on the default CRC setting, the current implementation gets
confused, and does not expect the correct signature for its packets.

Fix this, by ensuring that the ndp_sign member in the f_ncm structure
always contain a valid value.
Signed-off-by: Romain Izard <romain.izard.pro@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/function/f_ncm.c

@@ -35,9 +35,7 @@
 
 /* to trigger crc/non-crc ndp signature */
 
-#define NCM_NDP_HDR_CRC_MASK	0x01000000
 #define NCM_NDP_HDR_CRC		0x01000000
-#define NCM_NDP_HDR_NOCRC	0x00000000
 
 enum ncm_notify_state {
 	NCM_NOTIFY_NONE,		/* don't notify */
@@ -526,6 +524,7 @@ static inline void ncm_reset_values(struct f_ncm *ncm)
 {
 	ncm->parser_opts = &ndp16_opts;
 	ncm->is_crc = false;
+	ncm->ndp_sign = ncm->parser_opts->ndp_sign;
 	ncm->port.cdc_filter = DEFAULT_FILTER;
 
 	/* doesn't make sense for ncm, fixed size used */
@@ -805,25 +804,20 @@ static int ncm_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
 	case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
 		| USB_CDC_SET_CRC_MODE:
 	{
-		int ndp_hdr_crc = 0;
-
 		if (w_length != 0 || w_index != ncm->ctrl_id)
 			goto invalid;
 		switch (w_value) {
 		case 0x0000:
 			ncm->is_crc = false;
-			ndp_hdr_crc = NCM_NDP_HDR_NOCRC;
 			DBG(cdev, "non-CRC mode selected\n");
 			break;
 		case 0x0001:
 			ncm->is_crc = true;
-			ndp_hdr_crc = NCM_NDP_HDR_CRC;
 			DBG(cdev, "CRC mode selected\n");
 			break;
 		default:
 			goto invalid;
 		}
-		ncm->ndp_sign = ncm->parser_opts->ndp_sign | ndp_hdr_crc;
 		value = 0;
 		break;
 	}
@@ -840,6 +834,8 @@ static int ncm_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
 			ctrl->bRequestType, ctrl->bRequest,
 			w_value, w_index, w_length);
 	}
+	ncm->ndp_sign = ncm->parser_opts->ndp_sign |
+		(ncm->is_crc ? NCM_NDP_HDR_CRC : 0);
 
 	/* respond with data transfer or status phase? */
 	if (value >= 0) {